Opportunity cost

There is an opportunity cost in nuclear power: in terms of the fight against climate change, security of energy supplies and other considerations, nuclear power diverts
attention, effort, and large amounts of money away from renewables and
the conservation of energy, where those resources would be more effectively spent.

There is no valid justification for providing subsidies for nuclear power:

Nuclear power is a mature technology that should not require any subsidy. Subsidies are for newer technologies that are still finding their feet commercially.

There is abundant evidence from reputable sources that, in general, renewables, with conservation of energy:

Can provide greater security in energy supplies than nuclear power;

Are substantially more effective than nuclear power in cutting emissions of CO2;

Are cheaper than nuclear power, taking account of all subsidies;

Can be built much faster than nuclear power stations;

Can easily meet all our needs for energy, now and for the foreseeable future;

Provide more flexibility than nuclear power;

Provide diversity in energy supplies;

Are largely free of the several problems with nuclear power.

There is now a commercial race around the world to take advantage of the rapidly-growing market for renewable sources of power. We should be competing vigorously in that market, reaping the benefits in jobs and earnings. We should not be propping up a failed technology from the last century.

Here is relevant evidence:

Security of supplies:

Nuclear power is a hindrance, not a help, in ensuring security of energy supplies:

Like all kinds of equipment, nuclear power stations can and do fail. Failure of a nuclear
power station is very disruptive on the grid because a relatively large
amount of electricity is lost, often quite suddenly and with little
warning.

By contrast, variations in the output of renewables are much easier to manage because they are gradual and predictable.

Nuclear power is not a home grown source of power in the UK. All uranium is imported.

In addition, 6 other subsidies have been identified in the report Nuclear Subsidies (PDF). Some of these, such as the cap on liabilities for the disposal of nuclear waste appear to be quite substantial.

If we ignore those other 6 subsidies, then, as a very conservative estimate, the generation cost for nuclear power is 90 + 112 = £202/MWh, considerably more than the £140/MWh generation cost for offshore wind power.

Renewables can provide a diversity of sources of power, much greater than we have been relying on for most of the 20th century. In addition to two forms of solar power (concentrating solar power and photovoltaics), there is onshore and offshore wind power, hydro power, enhanced geothermal systems (EGS), biomass-fired generators, combined heat and power (CHP), wave power, and power from tidal streams, tidal lagoons and tidal barrages.

Renewables are largely free of the several problems with nuclear power, including the risk of nuclear disasters, the still-unsolved problem of
what to do with nuclear waste that will be dangerous for thousands of
years, and facilitating the proliferation of nuclear weapons.

Big day for renewables (WWF, blog by Bronwen Smith Thomas, 2011-05-09). "Only with much clearer signals from the government on ambition for
renewables will the clean tech industry be able to grow to its full
potential, bringing massive benefits to the UK economy. ... we need strong commitment to renewable energy from the
government in order to deliver the green economy. Nuclear power is an
expensive and risky option that could crowd renewables out of the
market."

In New Nuclear Power: Implications for a sustainable energy systemCatherine Mitchell and Bridget Woodman warn that “new nuclear power will not
contribute to the UK’s energy policy goals and, we believe, will
actively limit the UK’s ability to meet its climate change targets”.
This is because “the scale of the financial, political and institutional
commitments required to build new nuclear power plants will undermine
support for new technologies (such as renewable generation) and demand
reduction measures”.

"Nuclear expansion ... can’t deliver on its claims: it would reduce and retard
climate protection, because it saves between two and 20 times less
carbon per dollar, 20 to 40 times slower, than investing in efficiency
and micropower."Amory Lovins, writing in Grist, 2009-10-14.